FIG. 29 is a diagram schematically illustrating a configuration of a storage system.
A storage system 900 illustrated in this FIG. 29 is, for example, a RAID (Redundant Arrays of Inexpensive Disks) system including a plurality of storage devices arranged in an array, and is connected to a host computer 901, which is a higher-level device.
The storage system 900 performs processing, such as data reading or writing, on a storage device (illustration thereof is omitted) in accordance with an input/output request (e.g., read command or write command) from the host computer 901.
As illustrated in FIG. 29, the storage system 900 is configured to include a CE (Controller Enclosure) #000 and a plurality (two in the example illustrated in FIG. 29) of DEs (Disk Enclosures) #001 and #002. Further, the DEs #001 and #002 are cascade-connected (multistage-connected) in series to the CE #000. That is, as illustrated in FIG. 29, the CE #000 is connected to the DE #001, and the DE #001 is connected to the DE #002.
The CE #000 stores one or more (two in the example illustrated in FIG. 29) CMs (Controller Modules) #00 and #01. The CMs #00 and #01 perform a variety of controls in the storage system 900, and perform access control to each of storage devices provided to SAS expanders 802a, 802b, 803a, 803b, 804a, and 804b on the basis of an I/O (Input/Output) command transmitted from the host computer 901.
The CM #00 includes a controller 801a and the SAS (Serial Attached SCSI (Small Computer System Interface)) expander (EXP) 802a, and the CM #01 includes a controller 801b and the SAS expander 802b. 
The controllers 801a and 801b perform a variety of controls in the CMs #00 and #01, respectively. Further, in the CM #00, the controller 801a is connected to the SAS expander 802a via a data bus 811a, and is connected to the SAS expander 802b of the CM #01 via a data bus 812a. 
Similarly, in the CM #01, the controller 801b is connected to the SAS expander 802b via a data bus 811b, and is connected to the SAS expander 802a of the CM #00 via a data bus 812b. 
The SAS expanders 802a and 802b are connected to one or more common storage devices (illustration thereof is omitted), and perform access control to the storage devices on the basis of disk access commands transmitted from the controllers 801a and 801b. With each of the SAS expanders 802a and 802b connected to the one or more storage devices, the access path to the storage devices is duplicated.
The DE #001 is configured to include not-illustrated one or more storage devices and the SAS expanders 803a and 803b. With each of the SAS expanders 803a and 803b connected to the one or more storage devices, the access path to the storage devices is duplicated.
Similarly, the DE #002 is configured to include not-illustrated one or more storage devices and the SAS expanders 804a and 804b. With each of the SAS expanders 804a and 804b connected to the one or more storage devices, the access path to the storage devices is duplicated.
The SAS expanders 803a, 803b, 804a, and 804b perform access control to the storage devices on the basis of disk access commands transmitted from the controllers 801a and 801b. 
Further, the SAS expander 803a of the DE #001 is connected to the SAS expander 802a of the CE #000 via a data path 813a-1. Further, the SAS expander 804a of the DE #002 is connected to the SAS expander 803a of the DE #001 via a data path 813a-2.
Similarly, the SAS expander 803b of the DE #001 is connected to the SAS expander 802b of the CE #000 via a data path 813b-1. Further, the SAS expander 804b of the DE #002 is connected to the SAS expander 803b of the DE #001 via a data path 813b-2.
That is, the SAS expanders 802a, 803a, and 804a are cascade-connected in series to the controller 801a. In other words, as illustrated in FIG. 29, the controller 801a is connected to the SAS expander 802a, and the SAS expander 802a is connected to the SAS expander 803a. Further, the SAS expander 803a is connected to the SAS expander 804a. Similarly, the SAS expanders 802b, 803b, and 804b are cascade-connected in series to the controller 801b. That is, the controller 801b is connected to the SAS expander 802b, and the SAS expander 802b is connected to the SAS expander 803b. Further, the SAS expander 803b is connected to the SAS expander 804b. 
In the drawing, reference numerals attached with letters a and b indicate that there is a corresponding relationship between components designated by reference numerals attached with the same letter. For example, in the above-described configuration, the SAS expanders 803a and 804a are cascade-connected to the SAS expander 802a. Similarly, the SAS expanders 803b and 804b are cascade-connected to the SAS expander 802b. In the following, reference numerals attached with the same letter a or b will indicate that the components designated thereby have a mutually corresponding relationship.
Further, in the components with the above-described reference numerals attached with the letters a and b, if a component with a reference numeral attached with the letter a and a component with a reference numeral attached with the letter b have no difference in configuration and function, the components may be hereinafter designated by a reference numeral with the letters a and b omitted for the sake of convenience. For example, the SAS expanders 802a and 802b have the same configuration and the same function. In the following, therefore, the SAS expander 802 will represent the SAS expander designated by the reference numeral 802a or 802b. Similarly, the SAS expander 803 will represent the SAS expander designated by the reference numeral 803a or 803b. Further, the SAS expander 804 will represent the SAS expander designated by the reference numeral 804a or 804b. 
Further, in the data path from the controller 801 to the SAS expander 804, the side of the host computer 901, i.e., the side of the controller 801 may be hereinafter referred to as the upstream side or the higher level.
As the configuration management method performed in a storage system using SAS expanders for backend connection, as described above, a method is known in which the expanders issue an information frame called BROADCAST(CHANGE) (hereinafter referred to as BC(CHG)) upon detection of a change in configuration.
In the existing storage system 900 as described above, upon detection of a change in configuration, each of the SAS expanders 802 to 804 issues the BC(CHG) and notifies the upstream-side controller 801 of the detection. Thereby, notification to the higher level and reconstruction of the configuration are performed in the event of a change in configuration.
Further, the controller 801 and the SAS expanders 802 to 804 are capable of finding the respective connection states of devices subordinate thereto through a discovery process (see Japanese Laid-open Patent Publication No. 2008-197780, for example).
The discovery process is performed to allow the controller 801 and so forth to find the connection states of the subordinate devices when a change in state is detected in any of the SAS expanders. Specifically, the discovery process is performed with commands, such as REPORT GENERAL and REPORT ROUTE INFORMATION, transmitted from the higher-level SAS expanders 802 and 803 to the lower-level SAS expanders 803 and 804. The lower-level SAS expanders 803 and 804 transmit, as the responses to the above commands, the number of PHYs (PHYsical links) included therein and the information of the devices connected to the PHYs.
The controller 801 manages the information of the subordinate devices by using the information transmitted from the downstream-side SAS expanders.
In this type of storage system, however, if one of the plurality of cascade-connected SAS expanders is performing the discovery process, the SAS expander(s) and the controller higher than the SAS expander are unable to proceed with the discovery process. The state in which a SAS expander is performing the discovery process may be hereinafter referred to as the self-configuring state.
FIGS. 30 to 34 are diagrams for explaining processing performed when abnormality occurs during the discovery process in the existing storage system. For the sake of convenience, these FIGS. 30 to 34 illustrate one controller 801 and SAS expanders 802 to 804 cascade-connected thereto. Further, these FIGS. 30 to 34 illustrate, among the plurality of storage devices provided to the storage system 900, only one storage device 810 connected to the SAS expander 804.
In the storage system 900, if the SAS expander 804 detects a change (change in state) in the topology managed thereby, as illustrated in FIG. 30, for example, the SAS expander 804 transmits (issues) the BC(CHG) to the higher-level SAS expander 803, without performing the discovery process.
Further, the SAS expander 803 having received the BC(CHG) from the SAS expander 804 transfers the BC(CHG) to the further higher-level SAS expander 802, and the SAS expander 802 transfers the BC(CHG) to the further higher-level controller 801.
Each of the controller 801 and the SAS expanders 802 and 803 having received the BC(CHG) starts the discovery process, as illustrated in FIG. 31. Accordingly, the SAS expanders 802 and 803 shift to the self-configuring state.
The controller 801 and the SAS expanders 802 and 803 are unable to proceed with the discovery process when the subordinate SAS expanders 803 and 804 are in the discovery process state (discovery state) (self-configuring state), and thus shift to the standby state (discovery standby state, self-configuring state) (see FIG. 32).
That is, for example, the SAS expander 802 or 803 starts the discovery process after the subordinate SAS expander 803 or 804 has completed the discovery process (self-configuring) and transmitted the BC(CHG).
As illustrated in FIG. 33, however, the discovery process fails to complete in some cases, owing to some abnormality occurring in the SAS expander 803, for example. If the discovery process thus fails to complete in the SAS expander 803, the BC(CHG) is not issued from the SAS expander 803. Consequently, the higher-level SAS expander 802 is unable to receive the BC(CHG) and fails to complete the discovery process, remaining in the discovery standby state.
Further, even if the discovery process completes in the SAS expander 803, transmission path abnormality may occur in the transmission path 813-1, and thus the SAS expander 802 may be unable to receive the BC(CHG), as illustrated in FIG. 34. Similarly, even if the discovery process completes in the SAS expander 803, the SAS expander 802 is unable to receive the BC(CHG) if some abnormality occurs in the SAS expander 803 or 802, as illustrated in FIG. 34. If the SAS expander 802 thus fails to receive the BC(CHG), the SAS expander 802 and the controller 801 remain in the discovery standby state, and the discovery process is not completed.
That is, an issue arises in that the SAS expander 802 and the controller 801 remain in the self-configuring state and are unable to grasp the connection states of the devices subordinate thereto. In this case, the storage system 900 continues to operate while the SAS expander 802 and the controller 801 remain in the self-configuring state, and eventually the CMs are degraded, for example.
An object of the present case, which has been conceived in view of the above-described issue, is to allow, even if a storage device connection device does not return a response to an information acquisition request, a higher-level storage device connection device to continue to perform information gathering.
Objects of the present case are not limited to the above-described object. To provide an operational advantage which is derived from respective configurations illustrated in the later-described DESCRIPTION OF EMBODIMENTS, and which is not obtainable from existing techniques can also be regarded as one of the other objects of the present case.
According to a storage device connection device, a storage device, an information management method, and an information management program disclosed herein, at least one of the following effects or advantages is obtained.
(1) The state of standby for the completion of an information gathering process is cancelled to allow the completion of the information gathering process. It is thereby possible to perform the information gathering process also in a higher-level device.
(2) A storage device connection device with an uncompleted information gathering process is rebooted, and thereby is recovered from the state of information gathering process abnormality. It is thereby possible to stably operate the storage device connection device and a device connected thereto.